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Hydrol. Earth Syst. Sci. Discuss., 9, 9831011, 2012
www.hydrol-earth-syst-sci-discuss.net/9/983/2012/
doi:10.5194/hessd-9-983-2012
Author(s) 2012. CC Attribution 3.0 License.
Hydrology andEarth System
SciencesDiscussions
This discussion paper is/has been under review for the journal Hydrology and Earth System
Sciences (HESS). Please refer to the corresponding final paper in HESS if available.
Application of time domain inducedpolarization to the mapping of lithotypes
in a landfill site
A. Gazoty1
, G. Fiandaca1,2
, J. Pedersen1
, E. Auken1
, A. V. Christiansen1,3
, and
J. K. Pedersen4
1HydroGeophysics Group, Aarhus University, Denmark
2Department of Mathematics and Informatics, University of Palermo, Italy
3Geological survey of Denmark and Greenland (GEUS), Aarhus, Denmark
4Region Syddanmark, Vejle, Denmark
Received: 15 November 2011 Accepted: 6 December 2011 Published: 18 January 2012
Correspondence to: A. Gazoty ([email protected])
Published by Copernicus Publications on behalf of the European Geosciences Union.
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Abstract
A DC resistivity (DC) and Time Domain Induced Polarization (TDIP) survey was under-
taken at a decommissioned landfill site situated in Hrlkke, Denmark, for the purpose
of mapping the waste deposits and to discriminate important geological units that con-
trol the hydrology of the surrounding area. It is known that both waste deposits and5
clay have clear signatures in TDIP data, making possible to enhance the resolution of
geological structures, when compared to DC surveys alone.
Four DC/TDIP profiles were carried out crossing the landfill and another seven pro-
files in the surroundings, giving a dense coverage over the entire area. The whole
dataset was inverted using a 1-D Laterally Constrained Inversion scheme, recently im-10
plemented for IP data, in order to use the entire decay curves for reconstructing the
electrical parameters of the soil in terms of the Cole-Cole polarization model.Results show that it is possible to both resolve the geometry of the buried waste
body and key geological structures. In particular, it was possible to find a silt/clay lens
at depth, which correlates with the flow direction of the pollution plume spreading out15
from the landfill, and to map a shallow sandy layer rich in clay that likely has a strong
influence on the hydrology of the site. This interpretation of the geophysical findings
was constrained by boreholes data, in terms of geology and gamma ray logging. The
results of this study are important for the impact that the resolved geological units have
in the hydrology of the area, making it possible to construct more realistic scenarios of20
the variation of the pollution plume as a function of the climate change.
1 Introduction
Due to the expected climate changes, there is an increasing need to develop geo-logical models for predicting water flows in sensitive areas, such as former landfills.
Indeed, it is believed that groundwater fluctuations will become more extreme in the25
years to come. As a consequence, it would affect the time pattern and the intensity of
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precipitation, yielding dry summers and more rainfall in the winter season in northern
Europe (see some examples of scenarios in United Kingdom in Jackson et al., 2011;
Hulme et al., 2002). At some places where aquifers are strongly influenced by surface
water, this can lead to increased groundwater recharge and to a rising groundwater
table. In Denmark, many landfills operational between 1950 to 1980 were designed5
without any kind of capture system underneath, leading to percolation through the
waste and into the underlying geological layers and aquifer systems. In these cases,
the predicted changes in winter rainfall will probably increase the risk of leaching of
contaminants, which would, in turn, increase the outwash of chemical components
from landfills to nearby aquifers. Landfills without leachate collection systems thus pro-10vide a high risk to future groundwater quality due to changes in groundwater level. In
the light of these potential implications, it is important to have a fast, cheap and reli-
able technique which is able to depict the sub-surface at high resolution, both in landfill
areas and surroundings, and, if present, gain information on pollution patterns. Such
a technique involves the capability of characterizing waste deposits, but also the map-15
ping and identification of different geological units. Direct Current resistivity (DC) and
Time Domain Induced Polarization (TDIP or IP) have shown a good complementarity
in that respect. It is known that the conductivity of porous rocks varies with their wa-
ter content, ion concentration, mobility and the volume and arrangement of the pores.
The conductivity of rocks increases with the conductivity of their pore fluids, as well as20
higher saturation degree and fractional pore space. The surface conductivity becomes
important for materials with very large inner rock surfaces, such as clays (Kruschwitz
and Yaramanci, 2004). The specific electrical behaviour of clay is usually explainedby the presence of an external layer of cations in the so-called Electrical Double Layer
(EDL, see Revil and Glover, 1997; Revil and Leroy, 2004) at the surface of clay particles25
(platelets). The cations can easily move tangentially to the surface, and the resulting
surface conductivity contributes, together with the water volume conductivity, to the to-
tal conductivity (Tabbagh and Cosenza, 2007). Geophysical surveys have shown that
the contribution of the surface conductivity associated with clay minerals is often the
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dominant term in vadose and phreatic zones characterized by low mineralized waters
(Worthington, 1982). The induced polarization method has been used increasingly in
environmental investigations because IP measurements are very sensitive to the low
frequency capacitive properties of rocks and soils (Chen et al., 2008). These prop-
erties are associated with diffusion-controlled polarization processes that occur at the5
mineral-fluid interface (Slater and Lesmes, 2002). The IP phenomenon is often ob-
served in media with electrical resistivities typically lying between 50 and 100 m (the
most common values for soils, see Michot et al., 2003) and containing a significant
but non-dominant clay phase (Tabbagh et al., 2009). Usually, DC resistivity and IP are
used jointly in order to discriminate between materials displaying an identical signature10
in resistivity (e.g. brine and clay). Slater and Glaser (2003) showed from the results
of crosshole electrical imaging performed on sandy sediments, that high-resolution IP
measurements might be used to make a lithological description, allowing a differen-tiation between silt/clay and sands of different grain size. Kemna et al. (2004) used
the IP method in crosshole surveys in order to make a lithological characterization and15
to detect hydrocarbons. They also show how IP can significantly improve the under-
standing of the engineering properties of the subsurface relative to resistivity imaging
alone. Recently, Auken et al. (2011), Gazoty et al. (2011a, b) and Leroux et al. (2010)
have shown how the combined use of DC-TDIP could be successfully applied to land-
fill mapping and characterization, as it usually depicts the waste layer with a relatively20
high chargeable unit.
This study aims at delineating and characterizing the decommissioned Hrlkke
landfill and the waste body with high accuracy. It also shows how the joint applica-
tion of DC resistivity, IP and gamma ray logging enables a lithological description of the
global area to be constructed and depict different geological layers with variable clay25
content at high resolution.
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2 The Hrlkke area
In the CLIWAT project a test site has been selected for the study of a typical Dan-
ish landfill and the surrounding geology by geophysical methods, as input to improve
the knowledge for further modelling studies of hydrogeology and climate change sce-
narios. The area of interest is a decommissioned landfill, active from 1968 to 1978.5
It is located in the vicinity of Vojens, in southern Denmark (Fig. 1a), and covers an
approximate area of 10 000 m2
. The total amount of waste deposited is estimated to
be 65 000 m3
(Pedersen et al., 2009), mainly consisting of domestic waste and sludge
from Vojens wastewater treatment plant. Because the site was uncontrolled from 1972,some chemical waste from a refrigerator factory has also been dumped, but the amount10
remains unclear. The landfill was established without any kind of membrane, leachate
capture or isolation systems. All waste was dumped on the original terrain, yielding a
hillock approximately 15 m high. As a result of percolation through the landfill, contam-
ination has been detected below the landfill itself, and extending 500 m west as a deep
contamination plume (5060 m depth). At the landfill, the contamination is mainly com-15
posed of hydrocarbons, iron and inorganic compounds, as well as a small amount of
percolating chlorinated compounds. Within the plume, the contamination is composed
of a high concentration of volatile chlorinated compounds and inorganic parameters.
The Hrlkke landfill is located on a small outwash plain, and is located in a to-
pographic low, the general geology consisting of gravel and sand deposits, with local20
interbedded moraine clay layers (Fig. 2). At the landfill itself, the top layer consists of a
23 m thick clay filling layer, which covers the approximately 68 m thick waste layer.From a hydrological point of view, the sequence of sand layers (see Fig. 2) consti-
tutes a regional aquifer below the landfill. The aquifer reaches 100 m thick in some
places, and the water level is shallow, within 23 m depth. The area around the landfill25
has been pointed out as a special drinking water and extraction area for Vojens wa-
terworks (Pedersen et al., 2009). The landfill lies just west of the watershed, which
means there is no risk for drinking water with the current location. However, climate
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change could involve the shift of the watershed further east, so that the contamination
from the Hrlkke area might influence the water capture zone of Vojens waterworks.
This is why an initial hydrogeophysical characterization investigation is needed, as in-
put to constrain the geological models, and predict the different likely scenarios with
the highest accuracy.5
3 Materials and methods
3.1 DC and TDIP
The TDIP method measures the voltage decay induced by the turn-off of an exciting
current pulse (see Fig. 3) and uses the characteristics of the decay to study the induced
polarization of the soil, also known as chargeability. The equipment used in the field10
is the same as used for DC measurements, and thus the set-up consists of potential
and current electrodes equally distributed along a profile. Immediately after the current
is turned on, an induced potential, Vi, raises across the potential electrodes. After
a charge-up effect, the primary voltage, VDC, is measured for the computation of the
direct current resistivity (DC) just before the current is turned off.15
When the current is turned off, the voltage drops to a secondary level, Vs, and then
decays with time during the relaxation period. This decay curve is the target of the
Time Domain IP method, because it is characteristic of the medium, in terms of initial
magnitude, slope and relaxation time. The signal VIP along the decay is usually inte-
grated over n time windows, or gates, for the computation of the chargeability M, which20
is expressed as
M(t
)=
1
VDC [ti+1 ti]ti+1
ti
Vipd
t(1)
Where VDC [V] is the potential used for calculating the DC resistivity, Vip is the intrinsic
or secondary potential [mV], ti and ti+1 are the open and close times [s] for the gate
over which the signal is integrated.25
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3.2 Inversion scheme for DC-IP data
The inversion scheme used in this study enables the spectral content of the charge-
ability phenomenon to be extracted from time domain measurements. This spectral
information is contained in the time decays, and its description is obtained using the
Cole-Cole model (Pelton et al., 1978). The Cole-Cole model includes the DC resistivity5
and parameters describing the frequency dependency (c, and M0, see the section
below for further explanation). For each profile the whole dataset was inverted follow-
ing Fiandaca et al. (2011a), where the time domain forward response is computed via
a Hankel transform of the frequency domain response for a layered medium. Then,inversion is carried out with a 1-D-LCI implementation (Auken et al., 2005), to retrieve10
the four Cole-Cole parameters, for each layer. In the 1-D-LCI inversion algorithm, the
model is composed of a set of laterally constrained 1-D models aligned along a profile
(Auken et al., 2005). In practice, the LCI algorithm works by dividing a profile into sev-
eral individual 1-D models, with one dataset for each model. The model parameters of
layer resistivities/chargeabilities and depths are tied together laterally by claiming iden-15
tity between neighbouring parameters within a specified variance (Auken et al., 2002),
as illustrated schematically in Fig. 4.
3.3 The Cole-Cole model
There are a number of existing microscopic models that try to explain the IP phe-
nomenon, among which are the double layer (Leroy et al., 2008) and throat models20
(Titov et al., 2002). Despite this, the most popular IP model for field application re-
mains the Cole-Cole model, developed by Cole and Cole (1941) for the description of
complex permittivity behaviour. It is used by Pelton et al. (1978) to describe complex re-
sistivity. In the time domain, Pelton et al. (1978) showed that the intrinsic chargeability
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curves for Cole-Cole models in homogeneous media can be described by
M(t)=M0
n=0
(1)nt
nc
(1+nc)(2)
where [s], c [dimensionless] and M0 [mV/V] are the Cole-Cole decay parameters. M0is the magnitude of the chargeability taken at t=0, a time constant that characterizes
the decay and c a constant which controls the frequency dependence, and is bounded5
between the values of 0.0 and 1.0; is the Gamma function. In terms of physical
properties, M0 describes the magnitude of the polarization effect, and the relaxation
time, indicating, in the frequency domain, the position of the phase peak. Pelton et
al. (1978) and Luo and Zhang (1998) showed that M0 and depend on the quantity
of polarizable elements and their size, respectively, whereasc
depends on the size10
distribution of the polarizable elements (Vanhala, 1997; Luo and Zhang, 1998).
3.4 Boreholes-gamma ray logging
Since 1990, more than 25 boreholes with a depth of ca. 85 m have been established
near the landfill site (Fig. 1b) by reverse air rotary drilling for the collection of water
samples and for providing a thorough lithological description. Geophysical logging15
(natural gamma, induction, resistivity) has been performed in half of the boreholes
before casing. Each borehole was equipped with 46 screens over the depth from
approximately 10 to 80 m below surface. Subsequently, natural gamma logs have also
been performed inside the PEH casing in three boreholes.
The gamma ray logging (hereafter referred to as gamma log) measures the natural20
gamma radiation emanating from a formation. The major natural radio-isotopic sources
that contribute to the radiation are thorium, uranium and potassium (Kirsch, 2006). Al-
though there is no fixed rule regarding the amount of radioactivity for a given rock,
shales, clays and marls are generally several times more radioactive than clean sands,
sandstones, limestones and dolomites. In a given area, the only relative radioactivity25
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of the various rocks is of significance. The gamma log is extremely useful, especially
for discriminate among the different lithologies, because of its high vertical resolution.
Clays are usually sufficiently high in radioactivity because their cation exchange capac-
ity (CEC) allows to adsorb uranium and thorium. As a consequence, they can generally
be easily distinguished from the other rocks formation on a gamma log.5
Such types of borehole information is extremely useful to validate the results from
surface measurements. In this study, borehole descriptions were superimposed to the
2-D sections to check the consistency of the results, but no a priori information was
integrated to the inversion.
4 The survey10
The area was investigated with the collection of 11 IP/DC sections of 410 m, both on
top of the landfill and in the surroundings, all with an electrode spacing of 5 m (Fig. 1b).
The survey was performed using the gradient array (Dahlin and Zhou, 2006), which
was implemented on a Syscal-Pro instrument (Iris Instruments). The on and off-time
lengths for the time decay measurements were set to 4 s. The data were acquired15
using logarithmically spaced gates (Effers et al., 1999) with approximately eight gates
per decade, with a total of 20 gates. Four sections have been performed on the landfill
itself, all exceeding the landfill boundaries in order to cover both areas of low signal
and expected high signal. Six other profiles are located either at the edge of the landfill
or within the contaminated area, and one profile was set up outside the contaminated20
area to infer whether any different signature in IP/DC could be detected.
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5 Results
5.1 Landfill mapping
The inversion results for the four sections crossing the landfill are presented in Fig. 5.
Because of the relevance of the parameter M0 for depicting landfill areas, as shown
by Auken et al. (2011), it was chosen in this paragraph to show the results from this5
parameter only. Within the landfill area, the chargeability model can be divided into
three layers. The first layer on top is 3 to 5 m thick, with a chargeability of roughly
10 mV/V. Underneath, the second layer of 10 m thick displays a high chargeability sig-
nal up to 500 mV/V. The third deep layer in the model has a rather uniform chargeability
of 1030 mV/V. When comparing the models with the borehole information, there is a10
good match between these sharp boundaries and the different geological units. The
first layer of 10 mV/V in the topsoil agrees with a clay filling layer present in the bore-
holes. The third layer in the chargeability model more likely fits a sand layer (again
the top boundaries of the geological units and the model are completely consistent
between each other), which is responsible for the low chargeability signal from 20 to15
50 mV/V only. The high chargeable unit in between, of several hundreds of mV/V at 5
10 m depth, is laterally bounded within the anticipated landfill. Its depth and thickness
perfectly fit the waste body revealed by the borehole information. Although inverted
separately and independently (without any spatial constraints), the information content
provided by the four inverted sections is very consistent between each other. Note that20
the high chargeable features on either side of the landfill, going down to depth, are
most likely due to some topographic effects, as explained by Fox et al. (1980), and are
therefore of no consequence to the interpretation in this study.
Figure 6 shows 1-D models in chargeabilityM
0, from the inverted profiles P1, P11,P15 and P16, at two locations where they roughly cross each other (cf. stars in Fig. 1b).25
At each intersection, there is an excellent match between the sections, in terms of
depth, thickness and signal magnitude. A clear distinctive unit reaching 500 mV/V
enhances the waste layer at 10 m depth. These results agree with Auken et al. (2011),
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Leroux et al. (2010) or Carlson et al. (2001) who report a high chargeable unit related
to the waste body.
Because of the dense coverage of data across the landfill area and such a good fit
between all sections, it is possible to map and characterize the former landfill bound-
aries with a high accuracy, both in terms of thickness and lateral extent. Figure 7 shows5
gathered 2-D sections in M0 crossing and bounding the landfill. It enhances a perfect
agreement between crossing profiles, as well as a strong contrast in M0 between the
dump site and the close surrounding area (around 50 times higher). In order to clarify
the extent of the waste layer, an isovolume rendering of chargeability encompassed
between 100500 mV/V was added to the sections by following the method in Pryet10et al. (2011). This range of chargeability was chosen because this is the signal level
characterizing the waste body, as seen in Fig. 6. The isovolume with high chargeability
is 50000m3
big, which is in the same range of the a priori knowledge of the waste
dumped in the landfill (65000 m3
, after Pedersen et al., 2009).
5.2 Soil type discrimination15
We have seen in the previous section that the landfill mapping and characterization
could be done with high accuracy by the induced polarization method. Several profiles
were performed in addition outside the landfill area in order to improve the geologi-
cal description and clarify the presence of some specific patterns such as potential
clay lenses, both in the shallow and deeper parts. Indeed, from Fig. 2 it appears that20
some clay layers are expected at 5060 m depth, but the exact location in terms ofdepth and lateral extent remains unclear. It is, however, very important to gain knowl-
edge of the geological description in order to improve the hydrogeological models and
understand the flow pattern of the pollution plume. Care was taken to place the pro-
files on top of boreholes where possible, in order to correlate the information content25
provided by both methods. Results from profile 4 are presented in Fig. 8 with super-
imposed boreholes, for resistivity and chargeability. This profile is representative of
the main resistivity/chargeability features present in the other profiles carried out in the
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landfill surroundings, and the geological interpretation of the geophysical inversions is
presented in the next paragraphs.
5.2.1 Creek aquitard
In profile 4, within 150200 m from the north, a shallow conductive lens of about 60m
is present at 510 m depth (Fig. 8a). This lens is seen as a high chargeable layer of5
80 mV/V in chargeability (Fig. 8b), and perfectly fits the clay-till layer (in brown) re-
vealed by boreholes 151.1605, 151.1587 and 151.1477. Figure 9 shows a compari-
son between gamma logs performed in boreholes 151.1618, 151.1605, 151.1587 and
151.1477, and 1-D models of resistivity and chargeability fitting the same locations as
boreholes (note that borehole 151.1477 is not consistent with the other three, but the10
gamma log experiment was carried out many years after the drilling, with the casing in-
side. For this reason the gamma log curve is not reliable). Within 510 m depth, Fig. 9a
shows the good fit between the IP signal (high signal magnitude) and the gamma log,
which displays a high peak signal of 40 cps. In addition, Fig. 9b shows that a low re-
sistive layer is present at this depth, which is anti-correlated with the gamma log. The15
concordance of low resistivity/high chargeability with a high gamma log reinforces the
presence of a clay layer without ambiguity. The dense coverage in IP/DC enables to
define the lateral extent of this lens, observed from profiles 16 to 6 (not shown here).
Again, there is a good match in resistivity and chargeability where the 2-D sections
cross each other (e.g. between profiles 4 and 11). This clay layer underlies the Billund20
creek, which runs just north of the borders of the landfill, in the East-West direction.
Thus, this layer is probably an aquitard, acting as a bed of low permeability along the
aquifer.
5.2.2 Clay rich sandy layer
A moderately chargeable anomaly of less than 100 mV/V is present in the M0 section25
of profile 4 at 2040 m depth. This anomaly cannot be explained by the geological
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description of the boreholes, which report the soil at this depth only in terms of sand.
However, the signal level is present with different extents in all the other profiles of the
survey. As a matter of fact, purely sandy soil usually does not show high chargeability,
and consequently, no high values for M0. Between 20 and 40 m depth, Fig. 9a shows a
high chargeable layer fitting a high gamma log for boreholes 151.1605 and 151.1587.5
At this depth, Fig. 9b shows a high resistive content contrary to the shallow part which
is conductive. High gamma log and high chargeability usually indicate a significant clay
content, but the resistivity method allows in this case to make the difference between a
pure clay layer, which is expected to be conductive (as observed shallower, see para-
graph above), and a clay rich sandy layer, which is more resistive, as found between1020 and 40 m depth. This example demonstrates the complementarity of IP, DC resis-
tivity and gamma log, as the joint application of these three methods allows a detailed
recognition of the different geological formations.
5.2.3 Deep silt/clay lens
Within 125200 m from the north, profile 4 in Fig. 8 shows a more conductive feature15
at depth, reaching the basis of the section. This conductive bulk can be also observed
in the raw data. Considering a 400 m profile with a 5 m takeouts, the depth of the
feature remains on the ability of the DC method. This body can be considered as a
true and reliable pattern, even though it is located at depth. In addition a conductive
deep anomaly is present in all the other profiles going to the west, except profile 7.20
Figure 10 shows a 3-D plot of the resistivity models for all sections, with an isovolumein resistivity lower than 100m. This isovolume enhances a pattern which is near
surface in the vicinity of the landfill, goes deeper in the west direction and stops before
profile 7. Overall, the shape of this body has an extent of roughly 350 m, and, at some
places, a width of 120 m. The deeper part of this conductive anomaly fits well with25
silt/clay content in boreholes, as also shown in Fig. 8.
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6 Discussion and conclusions
The geophysical survey, together with the borehole information, allowed the recognition
and spatial delineation of several geological units important for the hydrology of the
area. In particular it was possible to map three key structures that influence the water
flow of the site: the clay layer that support the Billund creek north of the landfill; a5
clay-rich sandy layer at a depth of 2040 m, that likely exhibits a different hydraulic
conductivity when compared to the upper and lower clay-poor sandy soil; a silt/clay lens
at depth, that extends about 350 m west from the landfill and that likely supports the
flow of pollution in a westerly direction. A qualitative sketch of the survey findings that
summarize these geological units is presented in Fig. 11. The use of both DC and TDIP10
data, instead of DC measurements alone, greatly enhanced the resolution power of the
survey not only for the landfill delineation, but also for the characterization of the creekaquitard and for the recognition of the clay-rich sandy layer. In particular this last finding
is noticeable, because the DC data alone did not show any evidence of the enriched
clay content. These results are a perfect example of the potential of the IP method15
for hydrogeological studies and in landfill delineation, but more care is necessary in
the field to obtain a good data quality in comparison with the acquisition of DC data
only. The quality of the inverted sections presented in this paper can be attested by
the perfect match between all information provided by the 2-D sections wherever they
cross each other, even though each single section was inverted individually, without20
any spatial constraints. More importantly, the borehole information also allowed the
outputs of the geophysical survey to be verified, the match between the two being
excellent both inside and outside the landfill. The boreholes were also essential for
the interpretation of the geophysical results, mainly for the clay-rich sandy layer and
the silt/clay lens at depth. In our experience, the new inversion scheme adopted for25inverting the data also played a significant role in the success of the interpretation of
TDIP data. The detailed geological knowledge gained with the geophysical survey
is particularly important in the investigated area, where the presence of the landfill
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and the related pollution plume provide a high risk for the underlying aquifer. More
realistic scenarios of the variation of the outwash of chemical components from landfills
to nearby aquifers, as a consequence of the climate change, will be predicted when
incorporating such kind of information in the hydrogeological modelling.
Acknowledgements. This article is an outcome of the EU Interreg IVB project CLIWAT. It has5been co-funded by the North Sea Region Programme 2007-2013 under the ERDF of the Euro-pean Union.
References
Auken, E., Foged, N., and Srensen, K. I.: Model recognition by 1-D laterally constrainedinversion of resistivity data, in: Proceedings 8th meeting EEGS-ES, Aveiro, Portugal, 81210September 2002.
Auken, E., Christiansen, A. V., Jacobsen, B. H., Foged, N., and Srensen, K. I.: Piecewise 1DLaterally Constrained Inversion of resistivity data, Geophys. Prospect., 53, 497506, 2005.
Auken, E., Gazoty, A., Fiandaca, G., Pedersen, J., and Christiansen, A. V.: Mapping of Landfillsusing Time-domain Spectral Induced Polarization Data The Eskelund Case Study, 17th15European Meeting of Environmental and Engineering Geophysics (Near Surface), Leicester,UK, Expanded abstracts, E14, 1214 September 2011.
Carlson, N. R., Hare, J. L., and Zonge, K. L.: Buried landfill delineation with induced polariza-tion: progress and problems, in: Proceedings 14th meeting Symposium on the Applicationof Geophysics to Engineering and Environmental Problems (SAGEEP), Denver, Colorado,2047 March 2001.
Chen, J., Kemna, A., and Hubbard, S.S.: A comparison between Gauss-Newton and Markov-chain MonteCarlo-based methods for inverting spectral induced-polarization data for Cole-Cole parameters, Geophysics, 73, 247258, 2008.
Cole, K. S. and Cole, R. H.: Dispersion and absorption in dielectrics, J. Chem. Phys., 9, 34125351, 1941.
Dahlin, T. and Zhou, B.: Multiple-gradient array measurements for multichannel 2D resistivityimaging, Near-Surface Geophysics, 4, 113123, doi:10.3997/1873-0604.2005037, 2006.
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Effers, F., Auken, E., and Srensen, K. I.: Inversion of band-limited TEM responses, Geophys.Prospect., 47, 551564, 1999.
Fiandaca, G., Auken, E., Christiansen, A. V., and Gazoty, A.: Full decay forward response mod-eling and direct inversion for Cole-Cole parameters, submitted to Geophysics on June 2011,2011a.5
Fiandaca, G., Auken, E., Gazoty, A., and Christiansen, A. V.: Full waveform modeling of timedomain induced polarization data and inversion, Symposium on the Application of Geo-physics to Engineering and Environmental Problems (SAGEEP), Charleston, South CarolinaUSA, 1014 April 2011, SAGEEP 24 (140), doi:10.4133/1.3614087, 2011b.
Fox, C. R., Hohmann, G. W., Killpack, T. J., and Rijo, L.: Topographic effects in resistivity and10induced polarization surveys, Geophysics, 45, 7593, 1980.
Gazoty, A., Auken, E., Pedersen, J., Fiandaca, G., and Christiansen, A. V.: Reliability of Timedomain Induced Polarization data, Symposium on the Application of Geophysics to Engi-neering and Environmental Problems (SAGEEP), Charleston, South Carolina USA, 1014
April 2011, SAGEEP 24 (141), doi:10.4133/1.3614088, 2011a.15Gazoty, A., Fiandaca, G., Pedersen, J., Auken, E., and Christiansen, A. V.: Data repeatabil-
ity and acquisition techniques for Time Domain Spectral Induced Polarization, Near Surf.Geophys., under review, 2011b.
Hulme, M., Jenkins, G. J., Lu, X., Turnpenny, J. R., Mitchell, T. D., Jones, R. G., Lowe, J.,Murphy, J. M., Hassell, D., Boorman, P., McDonald, R. and Hill, S.: Climate change scenarios20for the United Kingdom: the UKCIP02 scientific report, Tyndall Centre for Climate ChangeResearch, University of East Anglia, Norwich, UK, 2002.
Jackson, C. R., Meister, R., and Prudhomme, C.: Modelling the effects of climate change and itsuncertainty on UK Chalk groundwater resources from an ensemble of global climate modelprojections, J. Hydrol., 399, 1228, doi:10.1016/j.jhydrol.2010.12.028, 2011.25
Kemna, A., Binley, A., and Slater, L. D.: Crosshole induced polarization imaging for engineeringand environmental applications, Geophysics, 69, 97107, 2004.
Kirsch, R.: Groundwater geophysics A Tool for Hydrogeology, Springer, 493 pp., ISBN 3-540-
29383-3, 2006.Kruschwitz, S. and Yaramanci, U.: Detection and characterization of the disturbed rock zone in30claystone with the complex resistivity method, J. Appl. Geophys., 57, 6379, 2004.
Leroux, V., Dahlin, T., and Rosqvist, H.: Time-domain IP and resistivity sections measuredat four landfills with different contents, 16th Eurepean Meeting of Environmental and En-
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gineering Geophysics (Near Surface), Zurich, Switzerland, Expanded abstracts, P09, 68September 2010.
Leroy, P., Revil, A., Kemna, A., Cosenza, P., and Ghorbani, A.: Complex conduc-tivity of water-saturated packs of glass beads, J. Colloid Interf. Sci., 321, 103117,doi:10.1016/j.jcis.2007.12.031, 2008.5
Luo, Y. and Zhang, G.: Theory and Application of Spectral Induced Polarization, GeophysicalMonograph Series No. 8, Society of Exploration Geophysicists, 171 pp., ISBN 1-56080-048-8, 1998.
Michot, D., Benderitter, Y., Dorigny, A., Nicoullaud, B., King, D., and Tabbagh, A.: Spatial andtemporal monitoring of soil water content with an irrigated corn crop cover using surface elec-10
trical resistivity tomography, Water Resour. Res., 39, 1138, doi:10.1029/2002WR001581,2003.Pedersen, J. K., Christensen, J. F., Poulsen, A. R., Wernberg, T., and Jacobsen, O. K.: Ned-
brydning af chlorerede oplsningsmidler I en dybtliggende forureningsfane vurderet pa bag-grund af vandanalyser og modellering, ATV Jord og Grundvand, 7182, 2009.15
Pelton, W. H., Ward, S. H., Hallof, P. G., Sill, W. R., and Nelson, P. H.: Mineral discriminationand removal of inductive coupling with multifrequency induced-polarization, Geophysics, 43,588609, 1978.
Pryet, A., Ramm, J., Chiles, J.-P., Auken, E., Deffontaines, B., and Violette, S.: 3D resistivitygridding of large AEM datasets: A step toward enhanced geological interpretation, J. Appl.20Geophys., , 75, 277283, doi:10.1016/j.jappgeo.2011.07.006, 2011.
Revil, A. and Glover, P. W. J.: Theory of ionic-surface conduction in porous media, PhysicalReview B, 55, 17571773, doi:10.1103/PhysRevB.55.1757, 1997.
Revil, A. and Leroy, P.: Constitutive equations for ionic transport in porous shales, Journal ofGeophysical Research, 109, B03208, doi:10.1029/2003JB002755, 2004.25
Slater, L. D. and Glaser, D. R.: Controls on induced polarization in sandy unconsoli-dated sediments and application to aquifer characterization, Geophysics, 68, 15471558,doi:10.1190/1.1620628, 2003.
Slater, L. D. and Lesmes, D.: IP interpretation in environmental investigations, Geophysics, 67,7788, doi:10.1190/1.1451353, 2002.30
Tabbagh, A. and Cosenza, P.: Effect of microstructure on the electrical conductivity of clay-richsystems, Phys. Chem. Earth, 32, 154160, doi:10.1016/j.pce.2006.02.045, 2007.
Tabbagh, A., Cosenza, P., Ghorbani,A., Guerin, R., and Florsch, N.: Modelling of Maxwell
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Wagner induced polarisation amplitude for clayey materials, J./ Appl./ Geophys./, 67, 109113, doi:10.1016/j.jappgeo.2008.10.002, 2009.
Titov, K., Komarov, V., Tarasov, V., and Levitski, A.: Theoretical and experimental study oftime domain-induced polarization in water-saturated sand, J. Appl. Geophys., 50, 417433,2002.5
Vanhala, H.: Mapping oil-contaminated sand and till with the spectral induced polarization (IP)method, Geophysical Prospecting, 45, 303326, 1997.
Worthington, P. F.: The influence of shale effects upon the electrical resistivity of reservoir rocks,Geophys. Prospect., 30, 673687, 1982.
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Fig. 1. The survey area. (a) Location of Vojens in the southern part of Denmark. (b) IP/DCsections (yellow dots) performed at the Hrlkke landfill (yellow area). The red dots point outthe boreholes, the white dots refer to gamma log locations. The location of the watershed isoutside the map. Copyright Cowi.
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Fig. 2. Simplified geological cross-section (see location in Fig. 1). The glacial sands (shallowred layer) host a regional aquifer. Modified from Pedersen et al. (2009).
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Fig. 3. Basic principles of Time Domain IP acquisition. The figure shows a sketch of the excitingcurrent and the resulting voltage.
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Fig. 4. Laterally Constrained Inversion (LCI) model set-up. The arrows represent the lateralconstraints. From Fiandaca et al. (2011a).
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Fig. 5. Inverted sections in chargeability crossing the landfill with superimposed boreholes.The landfill is located within the arrows.
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Fig. 6. Extracted models from the inverted surface measurements crossing the landfill. Thestars refer to the locations on the map in Fig. 1. (a) 1-D models from profiles 1, 11 and 16.(b) 1-D models from profiles 1, 11 and 15.
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Fig. 7. 3-D chargeability plot of the Hrlkke landfill. The isovolume map with chargeability(M0) above 100 mV/V allows to depict the landfill area without ambiguity.
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Fig. 8. Inverted sections for Profile 4 (see map in Fig. 1) with superimposed boreholes. (a) Re-sistivity section. (b) Chargeability M0.
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Fig. 9. Gamma logs (black) in comparison with 1-D models extracted from surface measure-ments. (a) Chargeability M0. (b) Resistivity.
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Fig. 10. Delineating the deep clay layer with the DC method: 3-D view of gathered resistivitysections with isovolume of resistivities lower than 100m. The anticipated extent of the plumeis drawn in purple.
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Fig. 11. Qualitative model obtained from geophysical measurements for a section crossing thelandfill from West to East (not at scale).
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